Buenos Aires -LRB- CNN -RRB- -- Police defused a bomb at a Buenos Aires theater Tuesday , a day before a former Colombian president was scheduled to speak there .

Authorities offered different assessments of the danger the explosive posed , and when it was set to go off .

A judge who investigated the Gran Rex theater said the bomb was set to be detonated around 4:30 p.m. Wednesday afternoon , when former Colombian President Alvaro Uribe is scheduled to speak .

`` It was a simple apparatus , but one that could have caused the death of people closest to it , '' Judge Norberto Oyarbide told reporters .

Later Tuesday , federal police said the bomb was designed more to cause commotion than serious damage , and had been set to go off on Tuesday afternoon , according to the state-run Telam news agency .

`` It was designed to produce shocking sounds , '' police spokesman Commissioner Nestor Rodriguez said .

A theater employee alerted authorities after finding the device , Oyarbide said .

`` Undoubtedly it looked like a bomb . You could see two pieces , and a cell phone , and it was connected in the middle , '' said Hector Fernandez , a theater employee .

Authorities were investigating to determine who placed it in the theater .

Colombia 's defense minister condemned the apparent attack attempt and called for an investigation .

Last week , a former top official from Uribe 's administration survived an assassination attempt -- a daylight bombing in Colombia 's capital .

Uribe was Colombia 's president from 2002-2010 , and was known for his focus on improving security and his tough stance on leftist guerrillas .

Uribe is scheduled to speak on at an international entrepreneurs conference Wednesday at the Gran Rex , one of the largest theaters in Buenos Aires .

A description of the event on the WOM Leadership Symposium 's website said Uribe would be discussing his role in `` the transformation of Colombia . ''

`` In 2002 , he found a country beset by guerrillas and overcome by uncertainty and despair . Eight years later , he handed over a country that was safe , thriving and respected by the international community as one of the most attractive countries for foreign investment , '' the website says .

A statement on the website said the conference would continue as scheduled Wednesday .

Human rights groups are planning a demonstration Wednesday afternoon near the theater to protest the former Colombian president 's participation in the symposium .

An announcement of the protest describes Uribe as a `` true threat to the region , '' arguing that `` in the name of the fight against ` terrorism ' he committed the most atrocious crimes against the Colombian people . ''

CNN 's Jose Manuel Rodriguez and journalist Fernando Ramos contributed to this report .

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NEW : Police say the bomb was designed to cause commotion

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Former President Alvaro Uribe is scheduled to speak in the theater

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Authorities are investigating to determine who planted the explosives

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Last week a former top Colombian official survived an assassination attempt in Bogota